Thermal pressure equalizer



Patented Sept. 23,1952

UNITED STATES PAT ENT F FYI-CE a 2,611,393 4 I I I THERMAL PRESSURE EQUALIZER Everett G. 'Gravenhorst, Hashrouck Heights, N. 3.,

assignor to Air Associates, Incorporated, Teterboro, N. -J., a corporation of New Jersey Application Mai-ch15, 1950, Serial No. 149,809

- V l Claim. 1

This invention relates to a thermal pressure equalizer for hydraulic fluid systems.

The invention primarily comprehends a thermal pressure equalizer which is adapted to be arranged in hydraulic systems connected with the landing gear of airplanes for imparting directional movement to the landint wheels when traveling on land and which is also adapted to be .arranged in shimmy damping systems employed in airplanes for reducing the oscillatory vibration imparted to the under-carriage and parts thereof in traveling over rough runways and the like. In such systems, the thermal pressure equalizer provides a means for taking up any sustained change of pressure therein due to change of temperature in the hydraulic fluid but which does not .react to any sudden change of pressure in the system or to pressure surges in the system due tooperation of the steering mechanism or resulting from oscillatory vibration or shimmy produced in the under-carriage or parts thereof. 7

An object of the invention is to provide a thermal pressure equalizer adapted to operate in systems in which the fluid is under relatively high pressure such as 1,500 pounds per square inch and which functions to reduce rupture of the system and the instrumentalities connected therewith caused by increase of pressure and volume resulting from rise in temperature of the fluid.

Another object of the invention is to provide a thermal pressure equalizer which functions to slowly relieve the system of pressure resulting from increase in temperature of the hydraulic fluid and to rapidly build up the pressure in the system upon decrease of temperature in the fluid.

Still another object of the invention is to provide a thermal pressure equalizer in which the flow of fluid from the system into the equalizer is relatively slow while the flowof fluid from the equalizer into the system is relatively rapid.

Still another object of the invention is to provide a thermal pressure equalizer having a poppet adapted to be moved to open relation to rapidly discharge fluid from the equalizer into the system and which is also provided with a relatively small orifice through which the fluid in the system flows into the equalizer.

With the foregoing and other objects in view, reference is now made to the following specification and accompanying drawings .in which the preferred embodiment of the invention is illustrated.

In the drawings:

Fig. :1 is a vertical sectional view of a thermal pressure equalizer constructed in accordaneewith the invention and shown with a pipe adapted to be connected in an hydraulic system and with the poppet disposed'in closed seatedrelation and the plunger moved to an elevated position by fluid from the system.

Fig. 2 is a similar view showing the poppet disposed in open relation and the piston moved to downward position with the forcing of the fluid into the system.

Fig. 3 is an enlarged vertical sectional view of the poppet and-valve.

Fig. 4 is a horizontal sectional view taken approximately on line 4-4 of Fig. 1.

Referring to the drawings by characters of reference, the thermal pressure equalizer includes a cylindrical casing l 0 having a threaded cap I! closing one end thereof and a sleeve 12 secured in the opposite end and which casing provides an elongated chamber 13 in'which a piston 14 is mounted for reciprocatory movement. 7 I

The equalizer is adapted to be connected in a fluid pressure system by a pipe 15 threadedly secured in the outer end of the sleeve 12 for admitting fluid to the chamber -13 between the piston 14 and a ring member 16. For this purpose, a poppet I1 is provided which is for-med with an enlarged cylindrical outer portion 18, a reduced cylindrical inner portion 48 and a restricted neck portion 20. The poppet I1 is formed with a bore 2| which opens through the opposite ends thereof, the outer portion 22 of the bore being relatively larger than the inner portion 23 and which inner and outer port-ions are joined by a constricted intermediate bore portion 24.

The enlarged outer portion 18 of the poppet is formed with a frusto-conical shaped portion 2i:

at the juncture with the constricted neck portion 20 thereof and adjacent thereto the restricted neck portion is provided with an outlet 26 through the side wall thereof. The'inner portion 19 of the poppet is formed with aligned openings '27 in which lugs 28 are secured and protrude therefrom so as to form projections for limiting the movement of the poppet toyopen relation. Arranged within the poppet H is :a tube 30 which extends from the bore portion 22 through the restricted intermediate bore portion 24 with'the inner end thereof protruding through the inner end of the inner bore portion 23. The said tube protrudes through "a plug '31 having a tapered the inside diameter of the tube 30 of .00035 of an inch on all sides thereof. Secured in the enlarged bore portion 22 of the poppet is a high a resistance porous element 35 which is spaced from the outer end of the tube 39 and which preferably consists of fused brass balls with minute interstices therebetween so as to permit of the passage of fluid therethrough upon sustained increase or decrease of pressure in the system.

The poppet I1 is mounted for reciprocatory movement in aligned central apertures 31 and 38 provided respectively in the sleeve l2 and in a bushing 39 located in the enlarged portion 40 of the central opening 4| extending through the ring 16. The opening 4| has its inner end portion reduced in size to provide the shoulder 42 against which the bushing 39 abuts and is secured in position within the ring [6. The inner end portion l9 of the poppet slidably fits the central aperture 38 in the bushing 39 while the cylindrical outer portion l8 of the poppet is spaced from the inner periphery of the central aperture 31 to permit of the flow of fluid from the equalizer through the aligned bore portions 23 and 24 and thence through the outlet 28 and into the central aperture 31 from which it is discharged through the pipe [5 into thejsystem. This takes place when the poppet I1 is moved to open relation, as illustrated in Fig. 2 of the drawings, which is limited in its movement by the lugs 28 engaging against the innerend of the bushing 39. The inner peripheral edge 43 at the juncture of the central aperture 38 with the outer face of the bushing 39, forms a valve seat against which the frusto-conical shaped portion 25 of the poppet engages to close off the flow of fluid from the equalizer, as illustrated in Fig. 1 of the drawings. The frusto-conical shaped portion 25 and the lugs 28 thus limit the reciprocatory movement of the poppet to closed and open relation respectively.

When in closed relation, as illustrated in Fig. l of the drawings, the fluid may flow from the system through the pipe l5 and thencethrough the high resistance porous element 36 and through the tube 30 into the portion of the chamber [3 between the piston 14 and the ring Hi. This takes place upon a sustained increase of pressure in the system due to increase of temperature in the hydraulic fluid. However, any sudden change of pressure in the system" caused by operation of the instrumentalities connected with the system, or due to oscillatory. vibration imparted to theunder-carriage of airplanes and parts thereof when arranged in a shimmy dampingsystem, would not operate to produce new of thefluid into the equalizer. The flow of the fluidthrough the high resistance porous element being restricted and the areaof flow between the inner peripheryof the tube 39 and the wire 33 being relatively small, further restricts the flow so that only by a sustainedincrease of'pressure such asoceasioned byrincrease of pressure 4. and volume upon a rise in temperature of the fluid, will fluid flow from the system into the equalizer.

The piston I4 is provided with an elongated stem 45 about which is arranged coil springs 46 and 41 interposed between the cap II and the piston 14 for tensioning the piston against the flow of fluid entering the equalizer. Upon any reduction of pressure or volume in the system below the pressure of the fluid in the equalizer, the poppet will be moved from the closed position shown in Fig. 1 of the drawings to the open position shown in Fig. 2 thereof, whereby the increased pressure in the fluid below the piston [4 will force fluid through the poppet as hereinbefore set forth. This movement of the poppet to open relation may take place rapidly so as to quickly discharge fluid into the system in the event of any sudden reduction of pressure or volume therein.

The area of flow of the fluid between the wire 33 and the tube 30 being so small, means must be maintained for preventing clogging thereof. This is accomplished by the wire 33 which has reciprocatory movement within the tube, the hook 34 limiting the inward movement thereof while the hook is also adapted to engage the porous element 36 to limit the outward movement thereof.

The sleeve I2 is secured in the outer end of the casing in any desired manner such as by a split ring 49 and screws 50 while the ring member 16 abuts at its inner end against the annular shoulder 5| formed in the inner periphery of the casing. The piston l4, sleeve l2, ring member l6 and bushing 39 are provided with packing rings 52 for preventing flow of the fluid about the outer peripheries thereof. The cap I l is provided with a vent 53 to permit of the escape and intake of air with the movement of the piston.

Constructed in this manner, a thermal pressure equalizer is provided which is adapted to operate in systems in which the fluid may be relatively low or in excess of 1,500 pounds per square inch, which functions to reduce rupture of the system and instrumentalities connected therewith by providing for the flow of fluid from the system into the equalizer whenever increase of temperature takes place in the fluid and which is adapted to rapidly discharge fluid into the system upon any sudden decrease of pressure and volume therein.

What is claimed is:

In a thermal pressure equalizer, a casing providing a fluid chamber, means defining a fluid passageway at one end of said casing and providing an annular seat forming a port, a poppet arranged in said fluid passageway for reciprocatory movement, said poppet having a frustoconical shaped portion adapted to engage said annular seat for closing said port, said poppet having a bore opening through the opposite ends thereof and an aperture in theside wall thereof communicating with the bore and with said passageway inwardlyof said seat when the poppet is seatedthereon, a restricted tube secured in said bore in open relation at its inner end with said chamber and said tube being spaced from the wall of the bore at its inner end to provide a passageway surrounding said tube and extending from said aperture through the inner end of said poppet and in communication with the chamber to permit of the rapid discharge of fluid from the chamber when the poppet is in open relation, and said restricted tube having an outlet at its outer end in'communication with the outer. end

of said bore to thereby permit of the flow of fluid UNITED STATES from the outer end of said passageway into said Number Name Date chamber through said restricted tube upon a sus- Re. 23333 Mercia, Jan. 23 1951 tained increase of pressure, and an elongated stifi 726 395 Bedworth et a1 28 1913 member loosely arranged in said restricted tube 5 2436:o09 Kremmer Feb 17 1948 for preventing clogging thereof. 2,462,929 Zodtner Mar. 1, 1949 EVERETT GRAVENHORST- 2,486,133 Egger Oct. 35, 1949 2,533,907 Anderson Dec. 12, 1950 REFERENCES CITED The following references are of record in the 10 file of this patent: 

